Space heater construction



"June 10, 1969 H K, GRAVES I 3,449,552

SPACE HEATER CONSTRUCTION Filed Oct. 11, 1965 I BV WW I JG m 12,

A T TORNEYS United States Patent 3,449,552 SPACE HEATER CONSTRUCTION Howard K Graves, Cleveland, Ohio, assignor to H. W. Tuttle & Company, Tecumseh, Mich., a corporation of Michigan Filed Oct. 11, 1965, Ser. No. 494,808 Int. Cl. H!) 3/06, 3/50 US. Cl. 219530 2 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a space heater construction and more particularly to a design for an electrical heating apparatus of the type which is mounted directly adjacent the wall of a room to be heated.

It is an object of the invention to provide a heat exchange unit which is designed for low-cost manufacture, simple installation and maximum efficiency.

It is a further object of the invention to provide a heater which can utilize relatively inexpensive and easily obtainable insulation which has a good co-efficient of thermal conductivity such that it may be used with a relatively moderate element temperature and yet provide excellent heating efficiency for the power input.

It is a further object of the invention to provide a construction wherein a Waterproof insulation material cooperates directly with a protective sheath which, because of the waterproof nature of the insulation, makes it possible to provide a single piece sheath with integral fins for creating a maximum air contact.

It is another object of the invention to provide a heating unit which transfers heat to the surrounding air in such a fashion that the elements can be mounted very close to the wall of a structure without any danger of overheating of the wall material.

It is another object of the invention to provide a unitized construction wherein the one piece metallic sheath and air transfer structure expands and contracts as a unit and thus is free of the noise which usually accompanies expansion and contraction in a compound heating unit.

Other objects and features of the invention relating to details of construction and operation will be apparent in the following description and claims.

Drawings accompany the disclosure and the various views thereof may be briefly described as:

FIGURE 1, a perspective view of the heating elements and mount showing one form of lead connection.

FIGURE 2, a side elevation of the structure shown in FIGURE 1 illustrating also a modified power lead construction.

FIGURE 3, an end view of the structure as shown in FIGURE 1.

FIGURE 4, a perspective view of one of the heat exchange elements.

FIGURE 5, a sectional view showing a construction for connecting a lead wire to a resistance wire.

FIGURE 6, a view of a metal blank cut to form a heat exchange element.

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REFERRING TO THE DRAWINGS The preferred type of linear heating element which may be used is formed with a coiled resistance element 30 preferably formed of Nichrome heater wire wrapped around a Fiberglas core 32. The heater element is then encased in a sheath of silicone rubber insulation 34, this material being a medium temperature material with a reasonably good coefficient of thermal conductivity and also having elastic properties and being Waterproof and characterized by a high electrical resistance.

Because of the characteristics above recited of the heating element and silicone sheath, it is possible to associate with the elongate heating element a heat transfer element which will extend along a wall of a space to be heated. Inasmuch as the metallic sheath can be provided for mechanical protection, but need not be waterproof because of the nature of the silicone coating, it is possible to form it in -a manner which is :both inexpensive and highly eilecive. This is accomplished by taking a strip of metal 36 as shown in FIGURE 6 having heat conductive properties such as sheet aluminum, this metal having, from the parallel side edges thereof, extending fins 38 formed by transverse slits 40 in the edges of the strip.

In the forming of the unit, the central portion of the strip 36 is shaped into a tube 42 to enclose the insulative sheathing 34 and the fins 38 are bent outwardly from the tube in a generally tangential disposition, each fin being rotationally :bent so that the planes of the fins are parallel with each other and perpendicular to the axis of the heater element. This formation spaces the fins at the outer ends to permit the ready passage of air vertically therethrough to accomplish efficient heat transfer. At the ends of the tubes 42, two short tabs 44 are formed and positioned together as shown in FIGURE 4 with holes 46 provided for mounting purposes. As shown in FIGURE 1, these tabs 44 are then riveted, bolted or welded to the short bracket ends 26 to support the entire structure on the mounting bracket B. The mounting bracket B comprises a mounting plate 20- with a right angle flange 22 having extending fingers 24, each of which has a bracket extension 26 lying parallel to the plate 20. Holes 28 are provided in plate 20 for convenient mounting of the entire supporting unit on a wall. The mountnig bracket can be used for the opposite end of the structure from that shown in FIGURE 1 by simply inverting it and similar brackets may also be used intermediate the ends in any desired spacing.

It will thus :be seen that the central portion 42 of the heat transfer metal can be shaped into the tube and compressed around the elastic silicone insulation 34 to insure a good heat transfer contact. It is not essential that the metal tube 42 be sealed along its seam because of the fact that it will provide ample mechanical protection if closed reasonably tightly about the silicone sheathing 34. In addition, the use of the many small fins which are closely adjacent each other and integrally joined with the tube 42 provides turbulant air flow for maximum convection of heat to the air. Because of this thermal efliciency the required heat transfer can be accomplished with lower than normal operating temperatures. This is a significant advantage inasmuch as there is less danger involved in a lower temperature and the insulating material has a significantly longer life. In addition, the rapid transfer of the heat from the integral fins prevents radial heat from reaching the adjacent walls on which the device is mounted and thus no special baflles or guards are needed between the heating elements and the mounting wall.

Another advantage is that the heater comes up to temperature rapidly because of the thermal efficiency and also cools ofi rapidly, thus having what is called a low thermal inertia characteristic. In addition, the absence of any welded joints in the unit avoids any cracking or expansion noise as the heater is raised to temperature and later cooled. Also, the vertical fins provide a very small area for the collection of dust and the heater remains clean.

A further advantage of the construction is the low manufacturing cost since the simple forming operations starting with a simple blank as shown in FIGURE 6 and the absence of any welding makes a very inexpensive unit.

In FIGURE 5, there is illustrated a means for connecting the heating elements to a lead wire. In this structure, the heating element is inserted into one end of a conductive terminal tube which has a recess to receive it at 52, the other end of the terminal tube receiving a lead Wire 54. The terminal tube can be crimped around the end of the resistance element 30 which, being disposed in a conductive tube, will be cool at this point. The terminal tube can also be crimped around the lead wire 54 and a suitable insulative material 56 is provided around the terminal tube as well as insulative protection 58 around. the lead wire 54. Thus, a secure, cool terminal is provided which is protected in the end of tube 42 and no enlargement of the lead wire or joint is necessary. The lead wires can then be clustered as shown in FIG- URE 1 and clamped in a crimped connector 60 along with a single lead wire 62.

A modified construction is shown in FIGURE 2 wherein the outer portion of conductive terminal tubes 50 are welded to a vertical bus wire 64 which has a single conductive strip 66 spot welded thereon. Then a lead wire 68 is fastened to the strip by a slip-fit metal envelope 70'. Here again, the structure can he duplicated at each end of the assembly.

It will thus be seen that there is provided an extremely efiicient, low cost space heating element which can be operated at several temperatures to provide effective and quiet heating. I

I claim:

1. An electrical space heating device comprising:

(a) at least two elongated electrical resistance elements each formed of a resistance wire wound on a core of electrically insulative material with a sheath of flexible electrically insulative material having relatively high thermal conductivity circumscribing said wire and said core,

(b) a heat dissipating element engaging and circumscribing each elongated electrical resistance element, said heat dissipating element comprising a single strip of heat conductive metal formed as a tube having abutting edges and a plurality of integral fins having root portions extending along said abutting edges and distal portions twisted to lie in spaced planes substantially transverse to said tube, said tube having at least one integral tab extending generally radially from at least one of said edges,

(c) at least one rigid mounting bracket having vertically spaced outwardly extending arms, each of said arms being connected respectively to one of said tubes through at least one of its associated tabs so that said heating elements lie in spaced apart overlying relationship to each other, and

(d) electrically conductive means electrically connecting saidresistance wires comprising electrically conductive connecting tubes with a portion of each tube telescoping over an end of each resistance element and engaging said associated wire and a portion telescoping over and engaging a lead wire extending outwardly from said connecting tube, and a common electrically conductive bus wire connected to each of said lead wires.

2. An electrical space heating device comprising:

(a) at least two elongated electrical resistance elements each formed of a resistance wire wound on a core of electrically insulative material with a sheath of flexible electrically insulative material having relatively high thermal conductivity circumscribing said wire and said core,

, (b) a heat dissipating element engaging and circumscribing each elongated electrical resistance element, said heat dissipating element comprising a single strip of heat conductive metal formed as a tube having abutting edges and a plurality of integral fins having root portions extending along said abutting edges and distal portions twisted to lie in spaced planes substantially transverse to said tube, said tube having at least one integral tab extending generally radially from at least one of said edges,

(c) at least one rigid mounting bracket having vertically spaced outwardly extending arms, each of said arms being connected respectively to one of said tubes through at least one of its associated tabs so that said heating elements lie in spaced apart overlying relationship to each other, and

- (d) electrically conductive means electrically connecting each of said resistance wires to a power connector.

References Cited RICHARD M. WOOD, Primary Examiner.

R. F. STAUBLY, Assistant Examiner.

US. Cl. X.R. 

